The present invention relates to a gland packing which can be preferably used in a shaft seal of a fluid apparatus or the like.
Conventionally, as a gland packing which can be used in a shaft seal part of a fluid apparatus or the like, for example, known is a gland packing 4 such as shown in FIG. 7. As shown in FIG. 6, the gland packing is braided (for example, 8-element square braided) by using a plurality of braiding yarns 3 each configured by a braiding yarn base material 6 in which a plurality of reinforcing fibers 2, 2 are embedded in the longitudinal direction in an expanded graphite tape 1 of a predetermined width with forming gaps in the width direction.
In the braiding yarn base material 6 shown in FIG. 6, however, the reinforcing fibers 2, 2 sometimes protrude largely from both or one of ends 1a, 1b in the width direction of the expanded graphite tape 1 which is cut into a predetermined width. In the gland packing 4 which is braided by using a plurality of braiding yarns 3 each configured by such a braiding yarn base material 6, the reinforcing fibers 2, 2 protrude from both or one of the ends 1a, 1b in the width direction of the expanded graphite tape 1 even after braiding.
In this case, when, as shown in FIG. 8, for example, in two braiding yarns 3 from which the reinforcing fibers 2, 2 protrude, the reinforcing fiber 2A protruding from one end 1a of the braiding yarn 3A, and the reinforcing fiber 2B protruding from another end 1b of the braiding yarn 3B overlap with each other, and the overlapping reinforcing fibers 2A and 2B are interposed over the whole range between the expanded graphite tapes 1 of the adjacent braiding yarns 3A and 3B and reach the whole range between the expanded graphite tapes 1 of the adjacent braiding yarns 3A and 3C, a large leakage path 5A is formed.
When the reinforcing fiber 2C protruding from another end 1b of the braiding yarn 3C, and the reinforcing fiber 2D protruding from one end 1a of the braiding yarn 3D overlap with each other, the overlapping reinforcing fibers 2C and 2D are interposed over the whole range between the expanded graphite tapes 1 of the adjacent braiding yarns 3C and 3D and reach the whole range between the expanded graphite tapes 1 of the adjacent braiding yarns 3D and 3H, a large leakage path 5B is formed.
In the gland packing 4 in which such leakage paths 5A and 5B are formed, the sealing performance is naturally largely lowered. As the number of the braiding yarns 3 is further increased to twelve, sixteen, or more, the possibility of formation of leakage paths is easily made higher, or the number of the leakage paths is easily made larger. This is not restricted to the gland packing 4 in which the plurality of the braiding yarns 3 are braided, and is applicable also to the gland packing 4 in which the plurality of the braiding yarns are twisted.
It is an object of the invention to provide a gland packing having a structure in which a phenomenon where reinforcing fibers protruding from ends of adjacent braiding yarns overlap with each other, and the overlapping reinforcing fibers are interposed over the whole range between expanded graphite tapes to form a leakage path can be reduced or prevented from occurring.
The gland packing of the invention is a gland packing of a braided structure where a plurality of braiding yams in which reinforcing fibers are embedded in an expanded graphite tape exist, wherein an end in a width direction of each of the braiding yams is directed to an inner side in the width direction of the braiding yarn.
In the thus configured gland packing of a braided structure, even when the reinforcing fibers largely protrude from ends in the width direction of the braiding yarns, the largely protruding reinforcing fibers can be directed or confined to the inner side of the braiding yarns because an end in the width direction of each of the braiding yarns is directed to the inner side in the width direction of the braiding yarn. Therefore, a phenomenon where reinforcing fibers protruding from ends in the width direction of adjacent braiding yarns overlap with each other, and the overlapping reinforcing fibers are interposed over the whole range between expanded graphite tapes of the adjacent braiding yarns to form a large leakage path can be reduced or prevented from occurring.
The other gland packing of the invention is a gland packing of a twisted structure where a plurality of braiding yarns in which reinforcing fibers are embedded in an expanded graphite tape exist, wherein an end in a width direction of each of the braiding yarns is directed to an inner side in the width direction of the braiding yarn.
Also in the thus configured gland packing of a twisted structure, in the same manner as the gland packing of a braided structure, the reinforcing fibers largely protruding from ends in the width direction of the braiding yarns can be directed or confined to the inner side of the braiding yarns. Therefore, a phenomenon where reinforcing fibers protruding from ends in the width direction of adjacent braiding yarns overlap with each other, and the overlapping reinforcing fibers are interposed over the whole range between expanded graphite tapes of the adjacent braiding yarns to form a large leakage path can be reduced or prevented from occurring.
Preferably, both the ends in the width direction of each braiding yarn are preferably directed to the inner side in the width direction of the braiding yarn. Even in the case of one end, however, the possibility of formation of a large leakage path is greatly reduced, and occurrence of defective products is greatly reduced.